Reset overload relay



3 Sheets-Sheet 1 INVENTOR @Wren ce//erce.

ATTORNEY March 26, 1940. 1 PIERCE RESET OVERLOAD-RELAY Original Filed Feb. 5, 1937 WITNE/SS@ M76 K.

March 26, 1940. L PIERCE 2,195,012

RES ET OVERLOAD RELAY Original Filed Feb. 5, 1957 5 Sheets-Sheet 2 fig? 4Z.

W/cf/ CONT/qc T5 /4 WITNESSES: INVENTOR i 0m/rence //er'ce.

ATTORNEY March Z6, 1940. L. PIERCE 2,195,012

RESET OVERLOAD RELAY Original Fi-led Feb. 5, v195'? .'5 Sheets-Sheet 3 WITNESSES: INVENTOR W' Lawrence Pierce.

W MBY ATTORNEY Patented Mar. 26, 1940 UNITED STATES RESET OVEBLOAD RELAY Lawrence Pierce, Pittsburgh, Pa., assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation o! Pennsylvania Application February 5, 1937, Serial No. 124,266 Renewed October l1, 1939 19 Claims.

My invention relates to thermostatic devices, and more Aparticularly to reset thermostatic overload relays for the protection oi electric devices.

One object of, my invention is to provide a thermal relay having novel resetting means for the relay after such relay has operated by reason of an overload.

Another object of my invention is to provide a thermal overload control relay that shall be eilicient in operation, veconomical to manufacture, small'in size, and easily installed.

A still further object of my invention is to provide a thermal relay having novel adjustable resetting means for the relay for controlling the time oi' resetting of said relay after such relay has operated by reason of an overload.

It is'also an object of my invention to provide a thermal relay with time-limit adjusting resetting means wherein the time-limit may be adjusted from a given time interval to larger time intervals including also time intervals of indeilnite length.

Other objects and advantages ci my invention will become more apparent from a study oi' the following speciiication and the accompanying drawings, in which:

Figure 1 is a view of one side of my thermal overload relay illustrated in combination with a diagrammatic showing of a line switch and a motor which the relay is to protect;

Fig. 2 is a sectional view of my invention taken on line II--II of Fig. l and looking inthe direction indicated by the arrows at the ends oi the section line;

Fig. 3 is a vertical sectional view of my invention taken at a region generally indicated by thev section line III-III shown in Fig. l;

Fig. 4 is a side view of my relay showing the side opposite to that shown in Fig. 1;

Fig. 5 is a sectional view similar to the sectional view oi Fig. 2 except that a certain feature is shown in adjusted position for a resetting time o! the relay of an indefinite time interval;

Fig. 6 is an exploded view of the thermostatic device of my relay, and includes a thermostatic4 disc and several elements associated therewith; and

Fig. 'l is a bottom view of the actuating plunger for the switch, or contact element, of my relay.

For a better understanding oi the objects of my invention, it is to be noted that in the cases where electric motors are used to drive pumps, compressors, etc., or any other apparatus likely to overload the motors, and wherein the operation of such motors may be controlled by a float controlled switch, a pressure responsive switch, thermostatically controlled switches, etc.,

it is necessary, when the overload relay operates to stop the motor in case of overload, that the overload relay remain in the operated, or tripped, position until manually reset in order to prevent the immediate restarting of the motor which would occur were the overload relay to automatically return to the non-operated, or reset, position with the switch in controls in the operating position. In many installations automatic restarting of the motor is desirable provided the time interval between the tripping of the overload relay and its operation to a reset position is of the desired length.

In the drawings, the reference character l designates a support, or base, of insulating material to which all the other members of the-relay are directly or indirectly secured. A thermostatic device generally designated by 2 and including, a disc element 3 of thermostatic metal, a retaining cylinder 4 having a shoulder 5, and a calibrating spider 6 secured in the cylinder and carrying the adjusting scew l, which screw is held in place by the lock nut 8, is secured in the support or base I by being held against the shoulder 9 by the securing member I il. The spider 6 is secured by press iit or other means in the cylinder 4 and holds the outer edge of disc 3 against shoulder 5.

The upper portion of the base I shows the switch terminal supporting lugs II and I2 to which the terminals I3 and I4 are suitably secured. These terminals are disposed to be connected to each other by the switch or contact element I5. This switch I5 is pivotally mounted on the spring I8 secured to the base I by rivets, or other means I1. A backing member I8 is disposed against the spring I8 to give it more rigidity at its point of flexure during operation.

A-threaded stud I9 is rigidly secured to the spring I6 at or near its mid portion and threaded button 20 of insulating material is mounted on the stud I9. The stud I9 and the button 20 have tightly engaging threads so that the position of the button 20 on the stud I9 will remain in the position to which it may be adjusted. It will be noted that the switch I5 may be caused to interrupt the interconnection of the terminals I3 and I4 when the button 20 is actuated toward the right. See Figs. 3 and 4.

In operation a suitable heater element 2i is secured in the opening at the right of base I and the motor current which flows through the heater element generates heat which is a direct function oi the amount oi current flowing. The heat so generated is transferred to the thermostatic disc, which may be of the type disclosed in the patent to John A. Spencer, No. 1,448,240, entitled Thermostat.

This disc has such characteristics that when the temperature is below a predetermined value.

the shape thereof may be substantially as shown in Figs. 3 and 'I of the drawings but when heated to a higher temperature of `predetermined value the disc will assume a reverse curve position with a snap action thereby moving button to the right, which movement is transmitted through stud I9 and spring I6. The spring is thus deflected in a clockwise direction (see Fig. 3) about the general region of the rivets I1. The connection established between terminals I3 and I4 is thus interrupted by the movement of the switch I5 toward the right.

The use of the relay is such that the operation of switch I5 in the manner explained opens the circuit for the electric heater element 2i whereby heat is no longer transmitted to the disc 3. As soon as disc 3 is cooled to a pren determined lower temperature, it snaps back into the position shown. The result is that the connection between terminals I3 and I 4`is reestablished. The time interval between the opening of the circuit between terminals I3 and I4 and the reestablishment oi' the circuit connection can be adjusted to some extent by the proper positioning relative to each other of the screw 1, and the disc 3. Normally, button 2D is adjusted on stud I9 to contact screw 1 after the switch I5 engages terminals I3 and I4. Ordinarily the thermostat is adjusted at the factory and operates'automatically to reset itself withing a fixed time interval, but when my relay is not arranged for automatic resetting, then the time of manual resetting of the relay is dependent on the will of the attendant. The resetting time oi' disc 3 is substantially constant for a constant ambient temperature but varies somewhat with the diderence in temperature between the ambient temperature and the tripping temperature of disc I. 'I'he time constant of the disc 3, even for a constant ambient temperature, may be varied somewhat by subjecting the disc 3 to an initial stress by a proper positioning o! screw 1 on the spider 6. The arrangement for automatic resetting may be effected by other means described hereinafter.

The heater is made so as to be readily changed to make the entire relay usable with motors of diierent ratings. i Ordinarily, the heater is not provided with a shunt but such shunt, comprising load 50 and resistor 5I, may be used as indicated.

From the description hereinbefore given, it is apparent that the relay operates automatically to open a circuit and to close the same circuit after a predetermined time interval. Ii the relay is to protect a motor, it is evident that the relay may be so connected that an overload will cause the relay to operate to disconnect the motor from its source of energy but since it resets itsel! the motor circuit will be reestablished after a short time interval. It the overload is still present, the relay will function again and again till the circuit breakers-operate. Such operation may be highly undesirable. The preferred operation may be such that the relay produces an eiIective restarting only if manually reset.

To accomplish the dual and selective effect of automatic andl manual reset, I provide the relay with a plunger 22. The plunger is circular in section for the major portion of its length and is disposed to slide back and forth in the base I. The plunger 22 is provided with two rectangular projections or lugs 23 and 24. The lug 23 projects out and beyond the face of the base I as shown at the slit in the base I. The projection or lug 24 projects beyond the face of the base but the base I is not provided with a slit at the right with the result that the inward movement of the plunger 22 is limited by the engagement of the lug 24 at the edge 2E. The lug 23 coacting with the slit 25 in the base permits reciprocatory movement of the plunger 22 but does not permit the turning oi the plunger.

The plunger has a spring 21 so that it tends to move the plunger outwardly. A ledge portion 28, less in height than the main portion of lug 24. is disposed beside lug 24. This ledge portion 28 engages the right-hand edge of spring I6 through ythe action of spring 21. When the thermostatic disc operates the spring I6 is moved clockwise (see Fig. 3) and in consequence, the switch I5 opens the connection between terminals I3 and I4 and the spring I6, being moved clockwise, permits the plunger 22, through the action of spring 21, to move toward the left (see Fig. 4). Plunger 22 is thus drawn under the spring I6 so that the lug 24 engages the right-hand edge of the spring. When the thermostatic disc snaps back to its original, or shown, position, the connection at the terminals I3 and I4 thus remains open, since the spring I6 remains on the ledge 28. If the connection is to be reestablished, the plunger must be moved inwardly-toward the right in Figs. 4 and 'I so that the spring I6 snaps ofi' the ledge 28 to the position shown.

The plunger 22 at the lug 23 is also provided with an incline plane portion which, when the plunger is manually actuated toward the right, see Figs. 4 and '7, may act like a wedge under the spring I6 to lift it to thus actuate switch I5 provided the plunger is moved toward the right a sufficient distance. The plunger thus acts as a stop switch as well as a means for manually resetting the relay.

From the description thus far given. it is apparent that the switch I5, in the absence of the plunger 22. automatically and in a selected time interval resets itself, that is, interconnects contact members I3 and I4, and with the plunger 22 the switch I5 is not automatically reclosed but may, even after the thermostat has reset itself automatically, be manually reset. In the absence of the plunger, there is no chance of using the relay also as a manually operable stop switch. In fact, when such automatic operation is contemplated, the spring I6 need merely be deflected a sufiicient distance to permit the projection 24 to pass under the spring I6. The plunger 22 and spring 21 may then be readily removed for storage in a convenient place.

When the relay is to have a substantially definite resetting time interval, and yet be operable as a stop switch by the plunger 22. the iiat retaining member 60 is positioned as shown in Figs. 2 and 4. This member 60 is secured to the base I at 6I and has the backing piece 62 to firmly hold it against the base I. The upper end of the member 6D is provided with a notch 63 adapted to coact with projection 23 to prevent the movement of the plunger 22 toward the left (see Fig. 4). When the plunger 22 is thus restrained, the thermostatic device breaks and makes the circuit at switch I5 and thus resets the relay automatically after a definite time as if the plunger 22 were not present, because the ledge 28 does not interfere with the movement of spring I6. The member 60 does, however, not prevent the inward movement of the plunger 22. The inclined portion 30 may thus cause the operation of switch I5 to stop the motor or other device protected by the relay.

When the relay is to function as manual reset only, the screw 64 may be turned to the position shown in Fig. 5. In such position, member 60 is so deflected that plunger Z2 is not restrained in its movements.

A still better understanding of my invention can be had from a study of its function in conjunction with a motor the invention is called upon to protect. In Fig. 1, buses 3| and 39 designate the source of energy for the motor 49. The accelerating controller-48 is shown schematically because it does not constitute part of my invention.

Il the motor is to be started, the starting Aswitch 32 is actuated whereupon a circuit is established from bus 3| through switch 32, actuating coil 33 of the line switch 34, conductor 35, binding post 3B, terminal I3, switch l5, terminal i4, binding post 31. and conductor 38 to the bus 39. Operation of the line switch 34 causes the closing of contact members 40 and 4|. The closure of contact members 40 establishes a holding circuit for the coil 33 so that switch 32 may be released. The closure of contact members 4| establishes a circuit for the motor 49, which circuit may be traced from bus 3| through contact members 4|, and conductor 42, binding posts 43 and 44, heater element 2|, binding posts 45 and 46, connected in parallel with adjustable resistor 5| and lead 50, conductor 41, accelerating controller 48, motor 49, to the bus 39.

The use of the four binding posts 43, 44, 45 and 4B, instead of only two vas 44 and 4 5, has the advantage that re-rating the relay by a change of the size of the heater element 2| does not disturb the motor leads connected to binding posts 43 and 46. Similarly, any change that needs to be made at the motor leads does not disturb the connections of the heater element.

If the motor is subjected to an overload for a predetermined time interval, the heater element will cause the disc 3 to snap to an opposite curvature than shown in Fig. 3 to thus open the circuit for coil 33 at the switch I5. The ledge 23 will move below spring I6 and thus prevent reestablishment of the circuit at the terminals I3 and |4. To restart the motor, the plunger 22 has to be moved inwardly manually a suflicient distance to permit the spring I6 to move counterclockwise (see Fig. 4) to close the circuit at switch l5 and also to expose the ledge 28 so that plunger 22 remains in the reset position. The circuit arrangement may be such that movement of plunger 22 to reset the relay is alone sufiicient to restart the motor or the arrangement may be as shown which requires also the operation of switch 32 to restart the motor.

If the member 60 is in the position shown in Figs. 2 and 4, theautomatic return of the thermostatic disc to its cooler position will restart the motor by the closing of switch I5 and the plunger 22 may be used as a stopping device. If the member is in the position shownjn Fig. 5, the relay, while still automatic in operation as far as its thermostatic feature goes, is manually reset. When the plunger 22 is removed, the relay is automatic only and cannot be readily actuated as a stop switch.

The disclosure herein made is believed to be illustrative of my invention and I do not wish to be limited'to the specific details illustrated and described but wish to be limited only by the claims hereto appended and such prior art as may be pertinent.

I claim as my invention:

l. An overload protective relay, in combination, a crescent-shaped heater element connected to be responsive to an electrical current, a discshaped thermostatic element disposed adjacent and substantially parallel to the plane of the crescent-shaped heater element and adapted to change its shape with a snap action when its temperature is increased by the heater element above a given relatively high value and adapted to resume its original shape when its temperature is decreased to a given relatively lower value, switching means operated by said thermostatic element to open the circuit to said heater element and said device, resetting means adapted to hold said switching means in open position, after having been caused to open by said thermostatic element. and means operating on said resetting means adapted to effect the automatic closing as well as the automatic opening of said switching means with changes in the shape of said thermostatic element. y

2. In an electrical control apparatus for electric devices, in combination, a switch spring biased to closed position, control means adapted to control the position of said switch, said control means comprising a thermostat for opening the switch when said thermostat is subjected to a given relatively high temperature, a switch operating member designed to occupy any one of three positions, which may be designated a left-hand position, a mid-position and a righthand position, means for moving the switch operating member to its left-hand position when said switch is operated to open position by said thermostat whereby said switch operating member maintains the switch in open position, means for holding the switch operating member out of the left-hand position whereby the thermostat may automatically open and close said switch as the temperature of the thermostat fiuctuates between a given high temperature and' a given lower temperature, and means for moving the switch operating member to the righthand position to thus effect the opening of said switch.

3. In a control means for an electric switch, in combination, a switch spring biased to closing position, a switch operating member designed to take any one of three positions which may be designated a left-hand position, a midposition, and a right-hand position, an electrical piece of apparatus carrying varying load currents, means responsive to the load currents of said apparatus adapted to automatically open and close said switch with variations in load currents from a given high value to a given lower value when said switch operating member occupies its mid position, said means responsive to the load currents of said apparatus also inltiating the operation of said switch operating member to its left-hand position when operated to the open position by a predetermined rise in load current of said apparatus, and means for operating said switch operating member to its right-hand position to open said switch.

4. In a control switch for controlling the operation of an electrical device, in combination, a source of electrical energy, a circuit for said control switch, means adapted to interconnect said circuit in circuit relation with said source of electrical energy, a contact element in the said circuit, means biasing said contact to circuit closing position. a thermostat having a heater element also connected in said circuit, said thermostat being adapted to move the contact element to such a position as to open the said circuit whereby the heater element becomes deenergized and the thermostat ceases to act on said contact element after a substantially definite time interval, a plunger biased to a given position which may be designated a lefthand position but held in a mid-position by said contact element when in closed circuit position, a latch ledge on the plunger adapted to hold the contact element in open circuit position once actuated to such position by the thermostat, and means on said plunger adapted to operate the plunger to one` position to thus remove said contact element from said ledge and permit said contact element to close, and in another position to positively hold said contact element open.

5. A switch element biased to a given position, a plunger so biased that a ledge on the plunger contacts the switch at one edge and is thus held in a mid-position by the switch element, means for moving the switch against its bias out of a given position and -out of the edge contact with the ledge on the plunger whereby the plunger, being biased as stated, moves to one side of the mid-position and in such manner that the switch element rides on the top of the ledge and thus remains' in its actuated position as long as the plunger is not moved to its mid-position, and means on said plunger adapted to also move said switch element against its bias out oi a given position, when said plunger is moved from its mid-position to the other side of the mid-position.

6. A switch element biased to a given position, a plunger so biased that a ledge on the plunger contacts the switch at one edge and is thus held in a mid-position by the switch element, means for moving the switch against its bias out of a given position and out of the edge contact with the ledge on the plunger whereby the plunger, being biased as stated, moves to one side of the mid-position and in such manner that the switch element rides on the top of the ledge and thus remains in its actuated position as long as the plunger is not moved to its mid-position, and means on said plunger adapted to also move said switch element against its bias out of a given position,rwhen said plunger is moved from its mid-position to the other side of the mid-position and adjustable means adapted, for one adjustment, to limit the movement of said plunger to its mld-position and to one side of the midposition.

7. A switch element biased to a given position, a plunger so biased that a ledge on the plunger contacts the switch at one edge and is thus held in a mid-position by the switch element, means for moving the switch against its bias out of a given position and out of the edge contact with the ledge on the plunger whereby the plunger, being biased as stated. moves to one side of the mid-position and in such manner that the switch element rides on the top of the ledge and thus remains in its actuated position as long as the plunger is not moved to its mid-position, and means on said plunger adapted to release said switch element and to also move said switch element against its bias out of a given position, when said plunger is moved from its mid-position to the other side of the mid-position.

8, In an electric circuit interrupter for interrupting a circuit including an electric device for protecting said device against overload, the cornbination of, a relay having switching means for opening said circuit, a reset plunger for manually operating said switching means to open circuit position. a snap-action thermostatic disc for operating said switching means, an electric heater element so connected as to carry a current proportional to the load current of the device to be protected, said reset plunger, having biasing means, so biased in relation to the relay switching means as to maintain the said switching means, after actuation by said thermostatic disc in open circuit position, and means for making the biasing means for said plunger ineffective.

9. The combination of thermally controlled means for overload protection of electric devices comprising a relay having a snap-acting bimetallic member, a heater element for the member, said heater element being adapted to heat the member as a function of the load current taken by the electric device to be protected, relay contact members adapted to be operated by the snap-action of the bimetallic member, a reset plunger so disposed in relation to the relay contact members as to maintain the latter in the tripped position when the said contact members have been actuated thereto until said plunger is manually actuated to reset position, and means for securing the plunger in the resetting position to thus provide for automatic resetting of the contact members.

i0. In an electric circuit intcrrupter for the protection of electric devices against overload. the combination of an electric circuit including a device to be protected, a relay having switching means for opening said circuit, a snap-action thermostatic disc for operating said switching means, an electric heater element so connected in said circuit as to carry a current proportional to the load current of the device to be protected. and a reset plunger so biased in relation to the relay switching means as to maintain the said switching means, after actuation by said thermostatic disc, in open circuit position.

11. In an electrical circuit interrupter. switching means biased to move to closed-circuit position, manually operable means for normally causing movement of said switching means to open-circuit position and to closed-circuit position, a current responsive element movable by energy taken from the electrical circuit upon the occurrence of a predetermined condition for applying a force to said switching means to move it to open-circuit position against its bias, and holding means for retaining said switching means in open-circuit position after movement to that position by said current-responsive element, said holding means being releasable to permit said siwitching means to return to closed-circuit posit on.

12. In an electrical circuit interruptor, switching means biased to move to closed-circuit position, manually operable means for normally causing movement of said switching moans to open-circuit position and to closed-circuit position, a current responsive element movable by energy taken from the electrical circuit upon the occurrence of a predetermined condition for applying a force to said switching means to move it to open-circuit position against its bias, said current-responsive element being operable to move the switching means to open-circuit position irrespective of the position in which said manually operable means may be held, and holding means for retaining said switching means in open-ciramavis cuit position after movement to that position by said current-responsive element. said holding means being releasable to permit said switching means to return to closed-circuit position.

13. In an electrical circuit interrupter, switching means biased to move to closed-circuit position, manually operable means for normally causing movement of said switching means to opencircuit position and to closed-circuit position, a current' responsive element movable by energy taken from the electrical circuit upon the ocurrence of a predetermined condition for applying a force to said switching means to move it to open-circuit position against its bias. said current-responsive element being thermally actuated to thus be operable, with changes oi ambient temperature, to move the switching means to opencircuit position irrespective of the position in which said manually operable means may be held, and holding means for retaining said switching means in open-circuit position after movement to that position by said current-responsive element, said holding means being releasable to permit said switching means to return to closed-circuit position.

14. In an electrical circuit interrupter, switching means biased to move to closed-circuit position, manually operable means for normally causing movement of said switching means to opencircuit position and to closed-circuit position, a current responsive element movable by energy taken from the electrical circuit upon the occurrence of a predetermined condition' for applying a force to said switching means to move it to open-circuit position against its bias, said current-responsive element comprising a bimetallic member acting with a snap-action to thus be operable, with changes of ambient temperature, to movethe switching means with a snap-action to open-circuit position irrespective of the -position in which said manually operable means may be held. and holding means for retaining said switching means in open-circuit position alter movement to that position by said current-responsive element, said holding means being releasable to permit said switching means to return i to closed-circuit position.

15. In an electrical circuit interrupter, switching means biased to move to closed-circuit position, manually operable means for normally causing movement of said switching means to opencircuit position, a current responsive element movable by energy taken from the electrical circuit upon the occurrence of a predetermined condition for applying a force to said switching means to move it to open-circuit position against its bias, said switching means remaining in open-circuit position when moved thereto by said current responsive means, and said manually operable means being movable to cause the return of said switching means to closed-circuit position.

16. In an electrical circuit interrupter, switching means biased to move to closed-circuit position, a single manually operable member for normally causing movement o! said switching means to open-circuit position, a current responsive element movable by energy taken from the electrical circuit uponthe occurrence of a predetermined condition for applying a force to said switching vmeans to move it to open-circuit position against its bias, said current-responsive element being thermally actuated to thus be oper- EST AVAILABLE COPY its able, with changes in ambient temperature, to move the switching means to open-circuit position irrespective of the position in which said manually operable member may be held, and holding means i'or retaining said switching means in open-circuit position after movement to that position by said current-responsive element, said holding means being releasable by movement of said manually operable member to permit said switching means to return to closed-circuit position.

17. In an electrical circuit interruptor, switching means biased to move to closed-circuit position, manually operable means for normally causing movement of said switching means to open- 'causing movement of said manually operable means to indicate the opening of the switching 'means and holding means for retaining said switching means in open-circuit position after' movement to that position by said current-responsive element, said holding means being releasable to permit said switching means to return to closed-circuit position.

18. In an electrical control device, in combination, a switch, biasing means adapted to normally hold said switch closed, control means, having a neutral or inoperative position and two operating positions. adapted i'or one operating position to open the switch and adapted for the other operating position to hold the switch open, biasing means i'or biasing the control means to the second operating position. means associated with said switching means adapted to maintain the control means in the inoperative position as long as said switch has not been opened but permitting free movement of the control means to the rst operating position, and further control means for opening said switch.

19. In an electrical control device, in combination, a switch, biasing means adapted to normally hold said switch ciosed, control means, having a neutral or inoperative position and two operating positions` adapted for one operating position to open the switch and adapted for the other operating position to hold the switch open, biasing means for biasing the control neans to the second operating position, means associated with said switching means adapted to maintain the control means in the inoperative position as long as said switch has not been opened but permitting free movement of the control means to the rst operating position, further control means for automaticaily opening and closing said switch, and means for making the biasing means for the first named control means ineiective to thus permit the automatic operation of said switch by said further control means.

LAWRENCE PIERCE. 

